The present invention relates to the field of valve shut off devices. More particularly the invention relates to a device for shutting off the fluid flow through a valve when excess pressure is sensed within the valve.
Although not limited thereto, it is contemplated that the present invention is to be used in air sampling systems of the type that monitor air from a closed compartment. Typically, when the air to be monitored contains harmful components, such as radiation or chemical compounds, it is drawn into a sealed container through a conduit from the generating location, measured for the particular constituents while in the container, and returned to the operating environment via another conduit. This type of monitoring system is a closed system and if excess pressure is allowed to build up within the system there can be catastrophic consequences on the sampling container and personnel. If the pressure becomes high enough, the container may leak or burst releasing the hazardous matter into the environment exposing personnel thereto.
Devices have been made for insertion into the conduits leading to and from the container for shutting off flow but each have limitations. Heretofore, flow has been shut off by utilizing electric solenoid operated valves in conjunction with separate pressure sensors in the system. These devices require electrical power and associated controls which make them more complicated.
Other devices for sensing pressure within the system, and for operating a shut off, include those that have a diaphragm for sensing differential pressure between the atmosphere and the system. While these devices do function to shut off flow when high pressure is sensed, they require that one side of the diaphram be vented directly to the surrounding atmosphere to establish a pressure reference. In the event of diaphram failure, the contaminants will be released directly into the atmosphere exposing personnel thereto.